Abstract B142: Multimorbidity and colorectal cancer–specific mortality in California, 2011–2021: A stratified analysis by race and ethnicity

Abstract Introduction: Colorectal cancer (CRC) is the third and fourth leading cause of cancer-related mortality in the United States (US) in males and females, respectively. While comorbid conditions are known to reduce survival in CRC patients, it remains unclear if this association varies by race and ethnicity. We examined the impact of multimorbidity on CRC-specific mortality among CRC patients diagnosed in California, stratified by race and ethnicity. Methods: We conducted a retrospective cohort study using data from the California Cancer Registry for adults diagnosed with CRC between 2011 and 2021. Multimorbidity burden was classified using the Charlson Comorbidity Index (CCI) into three groups: no comorbidities (CCI=0), low burden (CCI=1–2), and high burden (CCI≥3). We estimated subdistribution hazard ratios (sHRs) using Fine-Gray models, treating non-CRC causes of death as competing events. To further assess the cause-specific impact on CRC-mortality, we performed individual models for the 16 comorbidities considered in the CCI and an additional 8 selected comorbidities considered in the Elixhauser Comorbidity Index. Analyses were conducted stratified by race and ethnicity, with adjustment for age group, sex, marital status, nativity, neighborhood socioeconomic status, smoking status, stage at diagnosis and time from diagnosis to treatment. Analyses were performed using Stata 18.0 BE. Results: Between 2011 and 2021, a total of 163,480 individuals were diagnosed with CRC in California. Among them, 47,210 (28.88%) died due to CRC. Of these, 14,727 (31.19%) and 8,472 (17.95%) had a low and high comorbidity burden, respectively. In the multivariable model, compared to patients with no comorbidity burden, those with a low and high comorbidity burden had 6% (sHR=1.06; 95% CI: 1.03-1.09) and 28% (sHR=1.28; 95% CI: 1.24-1.33) higher hazard of CRC-specific mortality, respectively. When stratified by race and ethnicity, the adjusted sHRs for high comorbidity burden were 1.25 (95% CI: 1.18–1.31) among non-Hispanic White patients, 1.22 (95% CI: 1.07–1.37) among non-Hispanic Black patients, 1.31 (95% CI: 1.21–1.42) among Hispanic patients, 1.42 (95% CI: 1.27–1.57) among Asian/Pacific Islander patients, and 1.28 (95% CI: 0.84–1.94) among American Indian patients. Comorbid conditions most strongly associated with CRC-specific mortality were weight loss (sHR:1.74; 95% CI: 1.64-1.86), neurologic disorders (sHR: 1.39; 95% CI: 1.25-1.55), drug abuse (sHR: 1.27; 95% CI: 1.03-1.55), liver disease (sHR: 1.16; 95% CI: 1.08-1.25), congestive heart failure (sHR: 1.13; 95% CI: 1.04-1.22) and anemia (sHR: 1.09; 95% CI: 1.02-1.17). Conclusions: Our findings highlight the impact of multimorbidity on CRC-specific mortality among diverse racial and ethnic groups in California. Given the clinical relevance and high prevalence of comorbidities, integrated care and targeted public health strategies are essential to reduce disparities and improve outcomes in CRC patients. Citation Format: Diego Alvarez-Lopez, Joel Sanchez Mendez, William Hernandez, Lihua Liu, Mariana C. Stern. Multimorbidity and colorectal cancer–specific mortality in California, 2011–2021: A stratified analysis by race and ethnicity abstract. In: Proceedings of the 18th AACR Conference on the Science of Cancer Health Disparities; 2025 Sep 18-21; Baltimore, MD. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2025;34(9 Suppl):Abstract nr B142.